Brady-Tachy syndrome.

BRUPT CHANGES in the heart rate may be associated with a variety of symptoms. In the mid-eighteenth century, Morgagni,’ Adams,* and Stokes3 described a group of patients with intermittent slow or absent heart action and concomitant loss of consciousness, often culminating in death. Subsequent studies of this condition have identified a primary disturbance in atrioventricular conduction as a cause of the bradycardia, and the mechanism of syncope (Adams-Stokes syncope) may be either asystole or ventricular tachyarrhythmias complicating the heart block. Recently, a diverse group of patients with somewhat similar syncopal episodes but without atrioventricular block has been described in the medical literature. Disorders of sinus node function with atrial bradycardia and failure of subsidiary pacemakers to escape at a physiologic rate are the electrophysiologic abnormalities common to this group of patients. Descriptive terms such as sick sinus node,4-6 lazy sinus node, ’ inadequate sinus mechanism,8 sluggish sinus node,’ and sinoatrial syncope lo have been applied to the impaired sinus mechanism. An interesting and therapeutically challenging subgroup includes those patients with paroxysmal tachycardia complicating the atria1 bradycardia.“,” During the past 20 yr, more than 60 cases of